18,300kg methane per hour * 24 hours * 365 days = 160,308,000kg (~0.160 million metric tonnes). At 25x CO2 equivalent, that is 4,007,700,000kg (4 million metric tonnes).
This link about US electricity generation: https://www.eia.gov/tools/faqs/faq.php?id=74&t=11 shows 767 "million metric tons" from coal, or 1.55 "billion metric tons" from all sources.
4 / 767 ~= 0.5%, so in the ballpark of the parent comment. Also possibly the second link is ton (~1016kg) vs tonne (1000kg), further tweaking the numbers.
And just about the Permian basin, Wikipedia says it "accounts for 20% of US crude oil production and 7% of US dry natural gas production" - https://en.wikipedia.org/wiki/Permian_Basin_(North_America)#... So if all sites like this were measured, it might be more like 2.5% coal-use-equivalent?